Large in-plane/out-of-plane anisotropic conduction in PEDOT-based hybrid films: lamellar assemblies structured by mono-layered nanosheets

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a promising conductive polymer for electrical applications, and increases in its conductivity, transparency, stability, stiffness and strength have been explored. Herein, we demonstrate a facile fabrication method for a PEDOT film that exhibits large anisotropic conduction along in-plane directions. An aqueous solution of PEDOT added with polystyrene sulfonate (PSS) was mixed with an insulating oxide nanosheet based on montmorillonite (MMT) dispersed in aqueous media. Structural studies demonstrated it to be a hybrid film with a lamellar-like assembly that was structured with mono-layered sheets. In addition, an inhomogeneous mixture of pristine MMT (insulating) and PEDOT-rich (conductive) lamellar grains was proposed. The ratio between these two grains was controlled by tuning the content of the PEDOT:PSS solution in the initial mixing process. Increases in the content of PEDOT increased the electrical conductivity. This dependence is explained by a percolation model with random arrangements of PEDOT-rich conductive and insulating grains. The conductivity showed large anisotropy between in-plane and out-of-plane measurements. The ratio reached almost 10⁵ and remained the same over a wide range of temperatures. The lamellar structure of the PEDOT and nanosheets is ascribed to the large anisotropy.